Information relating to wheel-rail interactions of rail vehicles such as wagons can be used in various ways, such as to provide an indication of possible derailment of the vehicles, and analysis of wheel or track damage. However, it is generally not possible to make a direct measurement of the interaction forces between the wheels of a railway vehicle and rails on which the wheels are moving, because the contact locations are inaccessible.
A range of commercial products for indirectly determining these interactions are available, such as the software packages known as VAMPIRE®, ADAMS/Rail®, and NUCARS®. The products involve a forward dynamic model of the vehicle-rail system in which irregularities in the track are measured first and the contact forces are then predicted using the running speed and known properties of the vehicle. However, there are a number of disadvantages in the overall technique, including the cost of the measurement systems which provide the track data and their difficulty of maintenance for normal rolling stock.
A range of simulation packages which use (Artificial Neural Network) ANN modelling for rail vehicles and interaction forces are also available. These also require track geometry and running speed as input in order to calculate interactions between the wheels and the rails. An ANN model requires sufficient field test data to develop a simulation model for each vehicle type. The process is therefore costly and retains a limitation in that it depends on the most recent track data for daily evaluations of vehicle performance.
There has not yet been a successful product which is able to calculate wheel-rail forces in real-time, based on parameters of the vehicle and measurements of the motion of the vehicle. This is a non-linear inverse problem involving friction and damping in the wheelsets.